In recent years, there has been an increasing demand for color photographic materials having high image quality. Satisfying the demand requires multi-faceted and synthetic improvements of photographic characteristics embracing image structures such as sharpness and graininess, color reproducibility, tone reproducibility, and the like.
With respect to color reproducibility, there is a need not only to reproduce a hue with good fidelity but to reproduce a bright tone and more accurate. In order to achieve brighter color reproduction, so-called masking or an interimage effect has been utilized as disclosed in U.S. Pat. No. 2,521,908.
Details of an interimage effect are described, e.g., Hanson, et al., Journal of the Optical Society of America, Vol. 42, pp. 663-669 and A. Thiels, Zeitshrift fur Wissenschaftliche Photographie, Photoohysique und Photochemie, Vol. 47, pp. 106-118 and 246-255.
U.S. Pat. No. 3,536,486 discloses a method for obtaining an interimage effect by introducing diffusible 4-thiazolin-2-thione into an exposed color reversal element, and U.S. Pat. No. 3,536,487 discloses a method for obtaining an interimage effect by introducing diffusible 4-thiazolin-2-thion into an unexposed color reversal photographic element.
JP-B-48-34169 (the term "JP-B" as used herein means an "examined published Japanese patent application") describes that a marked interimage effect can be obtained by reducing silver halide to silver by development in the presence of an N-substituted-4-thiazolin-2-thion compound.
Research Disclosure No. 13116 (March, 1975) describes that a colloidal silver-containing layer is provided between a cyan layer and a magenta layer of a color reversal photographic element to obtain an interimage effect.
U.S. Pat. No. 4,082,553 discloses a method for obtaining an interimage effect in a color reversal photographic material having such a layer structure which permits migration of iodide ions during development wherein latent image-forming silver haloiodide grains are incorporated into one of the constituting layers, and latent image-forming silver halide grains and silver halide grains whose surface have been fogged so as to be developable irrespective of imagewise exposure are incorporated into another constituting layer In addition, JP-A-62-11854 (the term "JP-A" as used herein means an "unexamined published Japanese patent application") discloses an improvement in interimage effect of a color reversal photographic material which is brought about by addition of a 5-mercapto-1,3,4-thiadiazole compound.
Thus, color reproducibility and, in particular, saturation can be improved by enhancing an interimage effect. However, production of an interimage effect in excess results in insufficient reproduction of a delicate shade of color possessed by an original and reproduction of shade. Such a loss of gradation is considered to be due to absence or flattening of gradation of a complementary color in the image area where an original color should be reproduced, and this is a great evil of an interimage effect.
For example, when a red color is photographed, gradation of a cyan color is lost or flattened by a great interimage effect so that a bright red color is reproduced but, in turn, a delicate shade in the shade portion cannot be reproduced (so-called gradation loss of red). When a yellow color is photographed, cyan and magenta densities become low and flattened, making reproduction of bright yellow possible, but failing to reproduce a tone of the shade (gradation loss of yellow).
On the other hand, in the area where a bright red color should be reproduced, if a complementary color, i.e., cyan, becomes too hard, reproduction of a shade can be improved, but saturation is unfavorably reduced.
Thus, the exposure range where a complementary color is incorporated and the amount of the incorporated complementary color impact significantly on saturation and description of shades.
The above-described exposure range where a complementary color is incorporated and the amount of the incorporated complementary color can be adjusted to some extent by controlling interimage effect, spectral sensitivity distribution, and the like.
However, conventional techniques which have been proposed to date have found great difficulty in achieving strict control of these factors. Moreover, whether a given exposure range where a complementary color is incorporated and the amount thereof would be the most suitable for desired saturation and description of shades has not yet been determined.